All of the following biologic agents or diseases can be transmitted from person to person, EXCEPT:

All of the following biologic agents or diseases can be transmitted from person to person, EXCEPT:

• A. Smallpox
• B. Influenza
• C. Measles
• D. Ricin

Answer: (D)

The main idea is contagiousness: some agents are able to spread from one person to another, while others are not. Smallpox, influenza, and measles are contagious diseases that transmit through people—smallpox via close contact with lesions or contaminated materials, influenza through respiratory droplets or aerosols, and measles through airborne particles. Ricin, in contrast, is a toxin produced by the castor bean plant. It is not a living infectious agent and does not replicate or spread between people. You would only be exposed to ricin if you encounter the toxin itself (inhalation, ingestion, or skin contact), not from someone who has been infected. So ricin is the exception because it isn’t transmissible person-to-person.

The main idea is contagiousness: some agents are able to spread from one person to another, while others are not. Smallpox, influenza, and measles are contagious diseases that transmit through people—smallpox via close contact with lesions or contaminated materials, influenza through respiratory droplets or aerosols, and measles through airborne particles. Ricin, in contrast, is a toxin produced by the castor bean plant. It is not a living infectious agent and does not replicate or spread between people. You would only be exposed to ricin if you encounter the toxin itself (inhalation, ingestion, or skin contact), not from someone who has been infected. So ricin is the exception because it isn’t transmissible person-to-person.